Does anyone have any experience loading 45/70 rounds to subsonic velocities? I'm wonder how loud it would be?

I'm basically looking for a wisper quiet load, that I can have fun plinking with and not go deaf at a semi enclosed range. (I usually use subsonic .22 but 45/70 has so much more "fun factor")

I'm also curious if bullet weight will affect the sound level of the discharge . for example if I'm using the same powder charge to send a 500gr bullet out at 800fps and a 300gr bullet out at 900fps will one be quieter than the other?

It can be done; a few years ago there was some work done with subsonic .45-70 to avoid the transsonic transition at long range. It didn't accomplish much on target and I never saw the muzzle blast mentioned.

In olden times, there were "gallery loads" with the 250 grain "collar button" bullet. You might find some mention of them in an old book.

Do a search for Trail Boss powder. I've been using it for light loads in my 44 mag lever gun and my 8MM K-98. It turns that K-98 into a pop gun and is pretty quiet to boot. And a lot of people have been using it in 45-70 for light kicking loads.

I have looked up springfield loads and they are pretty light, but in general they are all supersonic, I had wondered about lightening them up further, but as counter intuitive as it might seem, I had heard that dangerous pressure spikes can actually occur when using too little powder in a cartridge.

There are a couple of sources of that. One is just getting below 50% case fill lets flame spread out over the powder when it lays sideways in the case, but the pressure doesn't usually get excessive from that unless the powder is very slow. It does, however, get erratic as the powder never quite lays the same way in the case each time.

Over the years there have also been reports of detonation that burst guns using charges that were less than 20% case fill. Usually it is reported with slow powders, though I found one online at a Finnish gunwriter's site that occurred to a .308 using 3.1 grains of Vihtavuori N320, a pistol powder about inbetween Bullseye and Unique in burning rate. The mechanism is not understood and has not been replicated in laboratory settings, so it apparently requires all the stars to line up just right. In small cases, like handguns, reports of detonation seem almost invariably to turn out to be accidental double charges. In the case of the N320 in the .308 that is not a plausible explanation, as the charge would have to be 7 times bigger just to reach normal .308 pressures.

For modern times, take advantage of IMR Trail Boss. It is much bulkier than the other powders, so you can load it down further by weight without the concerns. Details are here.

I've shot a bunch of 500gr@750fps plinkers from my Guide Gun. 7gr of Clays, WLR primer, no filler, no position sensitivity. They are not whisper quiet, but with ear plugs in most of what you hear is the CLACK of the hammer.

I have shot a lot of these out of my sharps that are as close to silent as you can get...not even as loud as an adult air gun..

My load is 4gr. of 4ffff black powder and then a .457 Round Ball in the shell. NO fillers needed and I have never stuck a ball in the barrel... shot them as far as 175yards and you can see them flying... they still had enough power to punch through the 1/2plywood dog house and bounce around inside..lol

The powder was set on top of the capacity reducer in the case.
The bullet was set on top of the powder.
The cartridge was gently lifted into the chamber while staying vertical
so the bullet would not fall off.
The action was closed and that forced the bullet into the lands.

1.0 gr Bullseye ..... shot with open sights at target at 27 yards, 2"
low and 1/2" to the right.

I could hear the bullet hit the brush and dirt.
If the same shots were fired into a piece of plywood, this would be an
extremely loud gun for the situation.

This was with a 22" barrel.
The primer alone will make a blam with a 5" barrel, so these figures are
for the effect of the powder charge on ~ 16" of barrel.
If a 32" barrel were used, the powder charges might well double to get
these sounds. The velocity would be higher.

When I still had a .45-70 one of my favorite loads was a 405 grn cast bullet at about 700-750 fps. This gave enought velocity to stabilize the bullet, but still was fairly quiet. You would still want ear plugs for extended range sessions, but for an occasional shot at a rabbit or armadillo, it didn't make much more racket than a .22

Since I've sold the gun, I can't remember the load, but I do know that it was published, so you shouldn't have much trouble finding one.

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